1. Field of the Invention:
This invention relates to a method and apparatus for the rendering harmless and cleaning of infectious plastic waste material, namely, used Petri dishes made of plastic. In this context, the term "rendering harmless" is to be construed as meaning "disinfection", i.e. killing pathogenic organisms to the extent required for practical purposes.
2. Prior Art:
Petri dishes are shallow round flat-bottomed dishes of transparent material which are used for microbiological culture processes, e.g. for culturing specimens of bacteria or other microorganisms. The microorganisms are cultured on a substrate which may be in the form of sterilized agar-agar that has been heated and poured into the dish and allowed to solidify therein to form a solid flat plate; the agar-filled Petri dishes are commonly referred to as agar plates. After the specimen to be cultured has been applied to the substrate, a close-fitting lid is placed on the agar plate which is then inserted in an incubator where a controlled atmosphere is maintained. When the culturing process is completed, the cultured specimen is examined while still on the substrate.
Present-day Petri dishes are almost always produced by injection molding of plastic (clear polystyrene) and used as a disposable article. It is presumed herein that the Petri dishes are made of plastic.
Since the cultured specimens may be pathogenic, the used agar plates must be handled such that the danger of transmission of infection is minimized. The handling therefore is rather laborious. Most microbiological laboratories consume large quantities of agar plates and in some laboratories the disposal of used agar plates is more or less a full-time occupation of one person.
The disposal of used agar plates often comprises collection of the lid-bearing agar plates in bags which are closed and placed in an autoclave in which the bag is subjected to a high temperature (well above 100.degree. C.) at elevated pressure. The bag with the now hopefully disinfected agar plates then is carried away to a refuse incinerating installation where it is burned. This way of disposing of the used agar plates not only is laborious and energy-consuming, but also leads to air pollution and destruction of valuable reusable plastic material.